Apparatus for the manufacture of pneumatic tyres



J. M. LOWE July 17, 1962 APPARATUS FOR THE MANUFACTURE OF PNEUMATICTYRES Filed April 28, 1958 3 Sheets-Sheet 1 h a "gil"l"llem July 17,1962 J. M. LOWE 3,

APPARATUS FOR THE MANUFACTURE OF PNEUMATIC TYRES Filed April 28, 1958 3Sheets-Sheet 2 fvg w J. M. LOWE July 17, 1962 APPARATUS FOR THEMANUFACTURE OF PNEUMATIC TYRES Filed April 28, 1958 3 Sheets-Sheet 33,044,533 APPARATUS FOR IfHE MANUFACTURE OF PNEUMATIC TYRES Jack MilnerLowe, Sutton Coldfield, England, assignor to Dunlop Rubber CompanyLimited, London, England, a British company Filed Apr. 28, 1958, Ser.No. 731,419 Claims priority, application Great Britain May 1, 1957 12Claims. (Cl. 156-401) This invention relates to apparatus for themanufacture of pneumatic tyres.

In the specification of co-pending patent application Serial No.696,156, filed November 13, 1957, now Patent No. 2,943,668 there isdescribed tyre building apparatus comprising a building drum andcylindrical supporting members located co-axially one at each end of thedrum to support the side portions of tyre building fabric extendingbeyond bead wires located adjacent to each side of the building drum. Aninflatable annular air bag is mounted on each supporting member, and asleeve is provided which is freely movable telescopically over the drumand each supporting member. Each of the sup porting members is providedwith an abutment for causing, upon inflation of the associated bagagainst the abutment and sleeve, movement of the bag and sleeve axiallywith respect to the drum so as to effect turn-over of the fabric aroundthe adjacent bead wire and onto the building surface of the drum.

It has now been discovered that ply turn-over apparatus of the kindreferred to in the preceding paragraph may be successfully operatedwithout the use of a freely movable telescopic sleeve providing thatsuitably designed annular air bags are utilised and it is an object ofthe invention to provide such apparatus.

According to the invention tyre building apparatus comrates atom prisesa collapsible building drum, cylindrical supporting members locatedcoaxially one at each end of the drum, an annular airbag carried on eachmember to support an end of tyre building fabric projecting beyond theend of the drum, each of said supporting members providing abutmentmeans for a portion of the inner wall of the air bag when inflated,whereby the upper wall is urged axially inwards to roll the projectingend of the fabric round a bead wire located on the fabric adjacent theend of the drum.

As in the apparatus described in said co-pending application Ser. No.696,156, now Patent 2,943,668 the thrust which, upon inflation of thebag, propels the air bag over the building drum is a function of theinflation pressure and the amount by which the efiective crosssectionalarea of the abutment exceeds the effective crosssectional area of thedrum plus the superposed tyre building fabric.

In the apparatus according to the invention it is preferable to use airbags which have been specially constructed, by the use of suitablerubber compounds and/ or fabric reinforcements, to resist undue radialexpansion, since the working pressure required to effect turn-over andto consolidate the turned-over plies might otherwise cause the bags toexpand sufficiently to distort the ply edges.

It will be appreciated that it is necessary to provide an annular airbag, for turning over the fabric, which has a circumference, takenaround an axial cross-section, of at least twice the length of thefabric to be turned over.

The abutment means may comprise a shoulder formed on each of thesupporting members'or may comprise an inflatable tube or tubes to form ashoulder upon inflation thereof. In one form of the invention the tubeor tubes is. or are surrounded bysegments which, upon expansion of thetube or tubes, assume a frusto-conical shape tapering towards thebuilding drum.

One embodiment of the invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIGURE 1 is an axial cross-sectional view of apparatus in accordancewith the invention;

FIGURES 2-8 are diagrammatic cross sectional views of the apparatus ofFIGURE 1 showing consecutive stages in its operation;

FIGURE 9 is an axial cross-sectional view of part of an air bag.

The apparatus comprises essentially a collapsible building drum 1 and apair of cylindrical supporting members 2 and 3 mounted co-axially one oneach side of the building drum and attached to a hollow supporting shaft4 by means of screws (not illustrated). The shaft 4 is carried in a pairof spaced-apart bearings mounted in pedestals (the bearings andpedestals are not illustrated) located outboard of one of the supportingmembers.

The collapsible building drum 1 comprises a cylindrical shell 5 uponwhich is mounted an annular fabricreinforced inflatable tube 6, andsurrounding the tube is located a lurality of rigid segments 7, eachsegment having a tongue 7a at each end which locates, in the collapsedstate of the drum with an annular surface 8,'

and with a second annular surface 9 when the drum is in the expandedstate. In the collapsed state the segments 7 are separated by a smallclearance space but otherwise surround the entire circumference of thetube 6. Each of the segments 7 is provided midway between its ends witha radially outwardly extending projection 7b. A resilient rubber sleeve10 of substantial thickness surrounds the segments 7, the outerperiphery of the sleeve 10 forming the building surface of the drum. Theinner periphery of the sleeve 10 has an annular slot 11 formed midwaybetween the end faces thereof within which the projections 7b on thesegments 7 are located to position the sleeve '10 axially.

Detachable rubber shoulder rings 12, having projecting ribs 12a on theirinner surfaces for engagement with corresponding grooves on the sleeve10, are fitted, one at each end of the sleeve 10.

The supporting members 2 and 3 are each of similar construction, and oneonly will therefore be described. The supporting member 2 comprises tworigid cylindrical shells 13 and 14 supported co-axially with thebuilding drum 1. A plurality of rigid segments 15, which in thecontracted state fit together in cylindrical form, surround the'shell14. These segments 15 constitute abutment means. The radially outwardmovement of the segments 15 is opposed by thin rubber bands (notillustrated) which surround the segments and are located in shallowgrooves in the segments. A pair of coaxial inflatable fabric-reinforcedtubes 16 is locatedbetween the segments 15 and the shell 14 and thetubes are inflatable via a common inflation tube 17 to expand thecylinder formed by the segments.

The" segments 15 are provided at their ends nearer to the building drumwith stop plates 18 for engagement with the inner surface of the shell13 to limit the radially outward movement of the said ends of thesegments. At the ends of the segments remote from the building drum theradially outward movement of each of the segments is limited by theengagement of the head of a bolt 19, attached to the segment, with astop 20 rigidly connected to the cylindrical shell 14. The segments 15,when fully expanded, take up a frusto-conical form (see FIGURES 4 I airbag 21 (see FIGURE 9) has a nose portion 22, which lies adjacent to thebuilding drum, the wall of which is of rubber of low tensile modulus,e.g. having 25% extension for a load of 70 lbs.;per square inch, whilstthe remainder 23 of the wall'of the bag is of rubber of higher tensilemodulus e.g. having 25 extension for a load of 140 lbs. per square inch.A ring 24 of expansible resilient rubber is attached to the bag asshown, for a purpose to be described, and an inflation tube 25 isattached to the bag in the conventional manner. The inside surfaces ofthe bag 21 are smeared with silicone grease and powdered with Frenchchalk, and the outer surface of the bag is graphited before cure. Beforecuring the bag, a loop of polyvinyl-chloride-covered metal wire (notillustrated) is inserted between the inside surfaces of the bag with oneof its ends projecting through the inflation tube and. the

other end overlying the hole through which the inflation tube passes.The loop extends towards the end 21:: of the bag 21 for approximatelyathird of the distance between the inflation tube and 'the said end.After the bag has been cured, the loop of wire, which during cure has'formed grooves in the inside walls of the bag for a purpose to bedescribed, is pulled out through theinflation tube. The wall thicknessof the bag 21 is A; of an inch, the outside diameter of the bag whenunexpanded and whenv carried on a supporting member is 12 inches and theexpanded diameter is approximately 15% inches.

In the assembled apparatus shown in FIGURE 1 it will be'noted that thediameters of the building drum 1 and adjacent portions of the supportingmembers in the collapsed state are slightly smaller than those of theouter surfaces of the remaining parts of the supporting members, and thebag shown in FIGURE 9 has been performed to conform to this shape. Theobject of this reduced diameter is to compensate for the increase inthickness resulting from the placing of an inner lining 26 and chaferstrips 27 on the drum 1 before the plies of tyre-building fabric areadded. The plies are thus laid on a substantially flat cylinder, whichhelps to maintain uniform ply joints. i

Theoperation of the apparatus just outlined in the manufacture of a tyrecover will now be described.

With the drum 1 and each of the'supporting members 2 and 3 in thecollapsed state, an inner lining 26 and chafer strips 27 are applied tothe drum as shown in FIGURE 1. A pairof plies 28 is then applied to thebuilding drum in the usual manner, side portions 28a and 28b of the pairof plies 28 extending one over each of the air bags 21 carried by thesupporting members 2 and 3 respectively. Bead wire assemblies 29 and 30are then passed over the plies from the free end of the apparatus andare located in position adjacent to the shoulders 12 of the buildingdrum.

The building drum is then expanded, as shown in FIG- URE 2," byinflating the associated tube 6, the bead wire assemblies 29 and 30 andthe chafer strips 27 being held inflation of the associated tubes 16through the common inflation tube 17, a shoulder forming portion 15athus being raised clear ofthe portion 13 of the supporting member.Pressure of the air bag 21 against this shoulder and against the axiallyprojected area of the frusto-conical surface formed by the segments 15causes the air bag to move automatically axially over the building drum,carrying with it the side portion 28a of the pair of plies 28. As the.air bag moves down the slope of the frusto-conical surface formed bythe segments '15; the resultant pressure causing the movement of the bagis progressively decreased, the frusto-conical form of the surface thuslimiting the tendency of the bag to overrun.

The low tensile modulus rubber nose portion 22 of the bag 21 conformsclosely to the profile of the bead assembly 29 as it rolls the pliesonto it and is anchored beneath the bead assembly 29 by the rubber ring24, thus ensuring good consolidation of the plies in the bead region.The overlying and surrounding portions of tyre-building fabric help toprevent excessive bulging of the portion 22 of the bag 21. The remainingportion 23 of the bag 21 of high tensile modulus rubber, and resistundue expansion of the bag under inflation pressure. 'An inflationpressure of 2%. lbs. per square inch has been found to give satisfactorythrust and consolidation of the tyre building fabric turned over.

When the bag 21 has rolled clear of the shoulder 15a the rolling actionceases (see FIGURE 5), in which position the edge 28a of the pair ofplies 28 has been turned over and pressed down firmly to the centralportion of the plies.

The bag 21 is then returned to its original position on the supportingmember 2 by deflating the tubes 16, thus rcturning the segments 15 tothe position shown in FIGURE 6, whereby the presure of the bag 21against the shoulder formed by the bead and ply assembly on the expandedbuilding drum 1 causes the bag to roll back from the building drum tothe supporting member 2. Deflation of the bag 21 commences during therolling back of the bag and is continued with the bag in the positionshown in FIG- URE 7, the final state of the bag on the supporting memher2 being shown in FIGURE 8. FIGURE 8 also shows the first stage in theturning over of the edge 28b of the ply, which takes place in a similarmanner to that describedfor the edge 28a.

When the type building operation is completed, the tube 6 of: the drum 1is deflated to cause the drum to assume a collapsed state and allowremoval of the built tyre cover.

During the rolling back of the bag 21 from the building drum, there is atendency for a ruck to be formed in the bag, particularly above theshoulder portion 15a where the bag is stretched during the ply turn overoperation. The tendency for rucks to form is reduced by the graphiteappliedto the inner surfaces of the bag as described earli er. When aruck is formed, there can be difliculty in deflating the air bag, andfor this reason grooves are provided on the inside surface of the bag,as described earlier, to allow air to escape past the ruck to the tube25.

In the use of the apparatus just described, the sequence of theoperations may be varied, for instance, the rolling bags may be inflatedafter instead of before the expansion of the segments on the supportingmember.

In an alternative construction, the bag has the same proportions as inthe embodiment just described and is of the rubber compound utilised forthe rubber nose thereof, the portion of the bag, apart from the nose,being reinforced by means of a knitted fabric, of steel or textilecords, having a known vlimit of stretch such that upon inflation of thebag the expansion thereof is limited to about 15% inches diameter. Sucha construction enables higher inflation pressures to be utilised.

In a further alternative air bag construction, the reinforcementconsists of a yarn of cotton-covered rubber thread, sold under theregistered Trade Mark Lastex, having appropriate stretch characteristicssuch that the required limited expansion is obtained.

Crimped :cords may also be used as a' bag reinforcement, the degree ofcrimping being such that upon expansion of the bag the expansion islimited by straightening of the cords.

In a further alternative embodiment of the invention in the case of eachsupporting member 2 and 3, the segments 15 are dispensed with and thetubes 16 are replaced by an expandable bag reinforced so as to becapable, upon inflation, of assuming a frusto-conical shape, taperingtowards the building drum, which will produce movement of the rollingbag towards and away from the building drum upon inflation and deflationrespectively of the expandable bag.

inflation of the air bags to an accurate predetermined pressure may beachieved by discharging a cylinder of air of known volume and at a knownpressure into the air bag.

Having now described my invention-what I claim is:

1. Tyre building apparatus comprising a collapsible building drum, anassembly of supporting members arranged in a cylinder located coaxiallywith said drum, one at each end of the drurn, an annular air bag carriedon said supporting members at each end of the drum to support the endsof tyre building fabric projecting beyond the ends of the drum, said bagwhen not inflated comprising a radially inner cylindrical wall on saidsupporting members and a radially outer wall on said inner wall, saidradially outer wall comprising a nose portion adjacent to said drum oflow tensile modulus compared with the remainder of the bag to expandover the end of said drum when said bag is inflated, each said assemblyof supporting members being expansible at the axially outer end thereofto a greater diameter than the portion at the inner end thereof and to adiameter greater than the diameter of the building surface of thebuilding drum, to urge the outer wall of the air bag, when the air bagis inflated, axially towards the building drum to roll the projectingend of the fabric around a bead wire located on the fabric adjacent theend of the 2. Tyre building apparatus according to claim 1 wherein thewall of each of the said air bags is composed of rubber of a low tensilemodulus reinforced with fabric, the expansion of each of the air bagsbeing limited to a predetermined value by means of the fabric.

3. Tyre building apparatus according to claim 2 wherein the fabricreinforcement is a knitted fabric.

4. Tyre building apparatus according to claim 1 wherein each of the saidair bags is provided, on the internal surface thereof, with a groovecommunicating with means for deflating the bag and extending axially toprovide means whereby, during deflation of the bag, air entrapped in aportion of the bag may be released through the groove to the said meansfor deflating the bag.

5. Tyre building apparatus according to claim 1 incorporating acollapsible building drum collapsible from a fully expanded cylindricalstate to a cylindrical state of reduced diameter, and air bags in whichthe radially innermost walls of the nose portion of each bag isthickened around its entire circumference, eaoh bag being disposed sothat the thickened nose portion extends over the end portion of thedrum.

6. Tyre building apparatus according to claim 1 wherein the collapsiblebuilding drum comprises a cylindrical shell having coaxially mountedthereon an inflatable annular tube, a plurality of axially extendingrigid segments surrounding the shell and tube, means for inflating thetube so that the overlying segments are disposed on a pitch circle ofincreased diameter, and a sleeve of resilient expansible materialsurrounding the segments.

7. Tyre building apparatus according to claim 6 wherein means areprovided at each end of each of the segments for limiting the radialmovement of the segments upon inflation of the said tube.

8. Tyre building apparatus according to claim 6 wherein a radiallyoutwardly extending projection is formed on each segment engaging withan annular slot formed on the inner periphery of the surrounding sleeveso as to locate the sleeve relative to the segments.

9. Tyre building apparatus according to claim 6 wherein a shoulder ringof resilient expansible material is detachably attached to an end of thesleeve.

10. Tyre building apparatus according to claim 1 wherein said supportingmembers are axially extending rigid segments located side-by-s-ide on acommon pitch cirdle, and comprising an annular inflatable tube locatedcoaxially within the segments, means for inflating said tube so that thesegments are disposed on a pitch circle of increased diameter, and meansfor restraining radially outward movement of the segments to a lesserdiameter at the end adjacent said drum than at the end farther from saiddrum so that the assembled segments take a frustoconical shape towardand coaxial with said drum.

l1. Tyre building apparatus comprising a collapsible building drum,cylindrical supporting members coaxial with said drum, one at each endof the drum and extending from an inner end adjacent ran-end of saiddrum to an outer end, each said supporting member being expansible to agreater diameter at its outer than at its inner end, and an annular airbag of expansible material for each supporting member, having one endadjacent the end of said drum and comprising a radially innercylindrical wall supported on said supporting member and a radiallyouter cylindrical wall supported on said inner cylindrical wall whensaid bag is not inflated, said outer wall comprising a nose portion oflow tensile modulus compared with the remainder of said wall so thatsaid nose portion will expand over the end of said drum when said bag isinflated, the outer cylindrical wall of each of said "air bags having alimit of circumferential expansion under fluid pressure sufiicient toexpand said nose over said drum and to form an axially movablesubstantially cylindrical wall spaced from said inner wall.

12. The tyre building apparatus of claim 11 in which each of saidsupports comprises longitudinal elements in cylindrical formation aboutthe axis of the support and stops to limit the radially outward movementof said elements at said inner end to a lesser distance than at theouter end to form a frusto-conical structure.

